This invention represents an improvement over such apparatus as disclosed in U.S. Pat. No. 3,424,116 issued Jan. 28, 1969 to W. R. von Hagen.
Thread trimming mechanisms fixedly secured beneath the sewing machine throat plate are most highly developed in the prior art as may be represented in the above mentioned patent. However, many of the thread cutters heretofore known, as well as the device found in U.S. Pat. No. 3,424,116 utilize a single moveable blade and a stationary blade associated therewith for severing the thread. In devices of this sort the moveable blade swings into the path of the needle thread and bobbin thread whereby seizing and drawing the threads over to the stationary cutter blade where the threads are cut. In devices of this sort there are certain drawbacks. One of the drawbacks incurred in using this type of device is the excessive length of the thread tail that is left depending from the garment. That is, when the moveable blade draws the threads over to the stationary blade the tail length depending from the garment will be increased due to this drawing action. Because of the excessive depending tail length a separate manual operation which entails cutting off the extra length is necessitated, thereby yielding an acceptable garment. However, this added manual operation adds time and thus cost to the garment manufacturer. Another drawback in utilizing a moveable blade with a stationary blade is that the synthetic threads employed today are more difficult to cut than the conventional cotton thread. In some instances, the cutting of synthetic threads is enhanced by means of a thread clamp which clamps the thread in place while the blade is operative thereon.
Although it is most desirable to provide a short tail length on the garment produced there is a definite need for a sufficient amount of bobbin thread to be present prior to the start of the next stitching cycle whereby assuring that the first few stitches in the following sewing cycle may be formed correctly.